Light sources for endoscopy or microscopy are known, and are marketed, e.g. by the applicant, under the name “D-Light System”.
Such light sources are used to illuminate an area that is to be inspected with an endoscope, for example. Since the area to be inspected is normally in complete darkness and since the light is usually supplied via light guides, which have only a small cross-section, the light source must provide light of high power or power density in order to ensure adequate illumination within the body. Arc lamps and, more particularly, so-called high-pressure xenon short arc lamps are generally used for this purpose.
In addition to producing a high output of light, such lamps generate a high output of heat. A present-day xenon short arc lamp with a total electrical power rating of 300 W emits less than 50 W as light and more than 250 W as heat. This heat must be drawn away from the lamp and out of the light source, as otherwise it may lead to overheating and damage to the light source.
Light sources of this kind have hitherto been cooled by transferring the heat generated by the lamp to a heat sink that has as large a surface area as possible. By means of fans located in the light source, air is guided through a housing of the light source and over the heat sink and thus carries the heat away from the housing of the light source. This is also referred to as active cooling.
Using fans in the field of medical applications is problematic, however, as such fans can produce layers of dust and dirt in the light sources, e.g. through abrasive wear or the leakage of lubricants. These layers of dust and dirt, particularly in a relatively warm environment of the kind found in the interior of a light source, are a breeding ground for potentially pathogenic bacteria. These bacteria are then in turn carried through the housing by the current of air and into an originally sterile area, where they lead to hygiene problems. The inside of the instrument is not normally cleaned on a regular basis, other than in the context of repairs.
Another problem is that known light sources use fast-rotating, and often non-sound-insulated, fans, which give rise to considerable, often monotonous, noise. Such noise is extremely disturbing to both the surgeon and the patient.